The present invention relates to a pick-up mechanism of a reproduction machine, such as a printing machine or a copier, especially of a wide-format printing machine, for controlling a pick-up cycle, and a method for performing a pick-up cycle in a reproduction machine.
Hereinafter, the invention will be described in the context of a wide-format printer in which a spring-biased pressure plate and a cam are used. Nevertheless, it is to be understood that it is equally applicable to other reproduction machines such as copiers, or other pick-up mechanisms.
In general, known printers use a spring-biased pressure plate and a cam to control the timing during the pick-up cycle of a pick-up mechanism for picking up a printing medium, such as a sheet of paper or transparency. A separate gearing mechanism is used to control the activation of the pick-up cycle by engaging with a main driving mechanism of the printer. The purpose of the spring-biased pressure plate and the cam is to allow media to come into contact with and to be fed by a pick-up roller in a timely cycle, and to allow a user to load media into an input tray of the printer between the pick-up roller and the pressure plate by creating a clearance therebetween.
FIGS. 1 and 2 show a gearing mechanism using the reverse pick-up concept to activate the pick-up cycle, as illustrated in a known printer, HP(copyright) DJ 1000, available from Hewlett-Packard Company, USA. The gearing mechanism comprises a control pinion 1 and a control cam 2 having a driving face 3 and a driven face 4, respectively, engageable with each other. The control cam 2 is in contact with a spring-biased pressure plate (not shown) to move the plate into a lower position (i.e. a position remote from the pick-up roller) and a raised position (i.e. a position closer to the pick-up roller) for engaging and disengaging a pick-up roller with/from a medium, respectively. The disadvantage of the reverse pick-up gearing mechanism is that the control pinion 1 has no total control on the movement of the control cam 2 during a complete pick-up cycle. When the pressure plate is about to rise up from its lowest position in the pick-up cycle, the upward force from the biased spring of the pressure plate causes the control cam to rotate at an uncontrolled speed being higher than the normal pick-up speed, since there is nothing to restrict the rotation of the control cam 2. The gearing mechanism is thus unable to receive the turning force of the control cam and disengage itself from the pick-up mechanism. This causes the pressure plate to rise up and hit, directly or, if medium is loaded, through the medium, like a paper stack, the pick-up roller uncontrollably at high speed, thus creating loud noises.
An object of the present invention is to provide a pick-up mechanism for controlling a pick-up cycle, and a method for performing a pick-up cycle in a reproduction machine, wherein noises are substantially reduced and the pick-up mechanism is able to pick-up the media at higher speed, thereby increasing throughput.
According to the present invention, the pick-up mechanism has a pick-up control pinion which is firmly coupled to a control cam, and a drive gearing including a first rocker driving gear and a second rocker driving gear which are mounted to a rocker device to be alternately engaged into and disengaged from, respectively, the pick-up control pinion. Upon starting the pick-up operation, the second rocker driving gear is drivingly engaged into a toothed section of the pick-up control pinion, and, in the course of the pick-up operation, the first rocker driving gear is drivingly engaged into the toothed section of the pick-up control pinion.
By arranging the rocker device it is possible to wholly control the rotation of the pick-up control pinion such that the movement of the pick-up control cam is also controlled during the whole pick-up cycle. The movement of the pick-up control pinion is controlled in a defined manner for the reason that the first and second rocker driving gear are alternately engaged into and, accordingly, alternately disengaged from the pick-up control pinion.
The above and other objects, features and advantages of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings in which like parts or elements are denoted by like reference signs.